Near-IR variability of the bulge stellar population

Variable stars in the near-IR can be used to characterise in detail the composite stellar populations of the Galactic bulge. Pulsating variable stars in particular (RR Lyrae, Miras, and classical Cepheids), are excellent distance indicators, as well as reddening probes. They sample the extremes of the Milky Way stellar populations: from the very old and metal-poor to the very young and metal-rich, passing through the intermediate-age stars. Their study has an impact on the fields of Galactic structure, stellar evolution, star clusters, and the interstellar medium, among others. I will cover the results on the pulsating variable stars in the complex environment of the Galactic bulge, concentrating mostly on the VISTA Variables of the Via Lactea Survey (VVV), that is a large ESO Public near-IR survey of the Southern Milky Way (http://vvvsurvey.org). In the first part of the talk I will describe the design, observations, data processing, and current status of the VVV Survey and its on-going extension VVVX. In the second part I will summarize the discoveries and latest results enabled by this and other large near-IR variability surveys of the Milky Way.